PHYSIOLOGICAL AND ULTRASTRUCTURAL-CHANGES IN ISOLATED WHEAT EMBRYOS DURING SALT AND OSMOTIC SHOCK

Physiological and ultrastructural changes were followed during early germination in isolated wheat embryos exposed to isotonic solutions of NaCl and sorbitol. Both NaCl and sorbitol entered the embryos, and imbibition during the first 4 h was similar. Thereafter, the increase in embryo fresh weight, respiration, and the uptake and incorporation of precursors into proteins and nucleic acids were strongly inhibited by NaCl while sorbitol only slightly reduced these aspects of metabolic reactivation. Electron microscopic observations also showed that the effects induced by NaCl were more severe than those produced by sorbitol. The results are discussed in relation to the previously observed lack of sodium toxicity in wheat embryos germinating within the intact seeds.